1. Field of the Invention
This invention relates to a light scanning device which is operative to scan a manuscript image in facsimile, for example.
2. Description of the Prior Art
Various types of the above mentioned light scanning device have heretofore been proposed. In a conventional light scanning device, a manuscript moving in one direction is illuminated with light emitted from a light source and the light reflected from the manuscript is projected through a projection lens onto a charge coupled device composed of a number of minute photoelectric conversion elements linearly arranged in a main scanning direction perpendicular to the moving direction of the manuscript, thereby scanning the manuscript. Such conventional light scanning device has drawbacks that since the projection lens is limited in its effective picture angle, the use of a manuscript whose width in the main scanning direction is 210 mm requires to separate the charge coupled device from the manuscript by a distance of 300 to 400 mm, thereby making the device large in size.
In order to eliminate such drawback, another light scanning device has been proposed and described in U.S. Pat. No. 4,149,197 in which the image of a manuscript is directly guided onto photoelectric conversion elements.
Such conventional light scanning device comprises a transparent substrate, an opaque member disposed on one of the surfaces of the transparent substrate and provided therein with a number of openings arranged along the main scanning direction for the manuscript and distant apart from each other by a given pitch, a number of photoelectric conversion elements disposed on the opaque member and formed of CdS, silicon or the like, each element having an opening aligned with each opening of the opaque member and having a size somewhat larger than that of the latter, and a transparent partition plate covering the upper surface of the photoelectric conversion elements. A manuscript disposed on the transparent partition plate is moved in an auxiliary scanning direction and illuminated with light emitted from a light source arranged at the other side of the transparent substrate. The manuscript image thus obtained is incident on each photoelectric conversion element, thereby scanning the manuscript.
In such conventional light scanning device, the light reflected from the manuscript is directly received by the photoelectric conversion element arranged at a position adjacent to the manuscript scanning position. As a result, it is possible to make the device as a whole small in size. But, such conventional light scanning device has drawbacks that each minute photoelectric conversion element must be provided with the opening, and that this opening is required to be precisely aligned with the opening provided in the opaque member, thus rendering the manufacture extremely difficult. In addition, the manuscript is illuminated only with the light passed through the opening provided in each photoelectric conversion element and each photoelectric conversion element is provided at its center portion, where the light reflected from the manuscript is incident in the most efficient manner, with the opening so that that portion of the photoelectric conversion element which is provided with the opening receives no reflected light, thereby rendering the efficiency of utilizing the illumination light bad.